This invention relates generally to rotating electrical machinery, and more particularly to a self-ventilated electrical machine with an axial-flow fan and a ventilator encasing associated with the fan.
In conventional electrical machines with axial-flow fans, the clearance between the fan blade and the encasing associated with the fan are kept as small as possible in order to avoid pressure losses. Generally, the clearance is approximately 0.5 mm. However, maintenance and disassembly work in which the rotor of the machine has to be lifted, such as maintenance work involving the bearings, require substantially more clearance for motion between the fan and the encasing. As a result, maintenance and disassembly work generally require extensive and time-consuming measures in order to disassemble the encasing or to regulate the position of the encasing with respect to the fan. Such measures often include breaking through the machine casing in order to reach the ventilator encasing.
It is therefore an object of this invention to provide an electrical machine with an axial-flow fan and a ventilator encasing which facilitates maintenance and disassembly work.
According to a preferred embodiment of the present invention, the encasing includes two encasing parts, one of which is axially moveable with respect to the axial-flow fan blade. The axially moveable encasing part can be moved away from the fan blade to facilitate maintenance and disassembly work. The non-moveable encasing part is fixedly connectly to the machine casing or to stator sheet-metal plates of the machine. The moveable encasing part is moveably mounted on a bearing bracket associated with the rotor shaft of the machine and with the machine casing, and can be removed together with the bearing bracket from the machine. The moveable encasing part is so mounted on the bearing bracket that the moveable encasing part can be moved away from the fan blade even when the bearing bracket is fixedly connected to the machine casing.